1. Field of Invention
The present invention relates to a recording media storing an audio/video program and a method for playing the audio/video program. More specifically, the present invention relates to a recording media storing a subtitle data structure of the audio/video program and the method for displaying the subtitle data of the audio/video program.
2. Description of Related Art
Among various recording media, a compact disk (CD) is characterized with the advantages of its high capacity, low cost and portability, etc, and thus has been widely used in many different fields including storing data, listening music and watching movies. To be adapted for the characteristics of the CD and increase the reliability of reading CD data, when storing data on a pre-recording CD, if the encoded data is 1, then the recording surface with an organic dye is directly heated by a laser beam (775 nm˜795 nm) output from a high power semiconductor laser, thereby burning the recording surface to form a data pit, whereas, if the encoded data is 0, no data pit is formed.
When a CD player reads the CD at a lower power laser beam, since the data pit and the un-burnt recording surface of the CD have different reflection indexes, the data pit absorbs a portion of the laser beam, while the un-burnt recording surface doesn't absorb the laser beam so that the CD player can reproduce the original encoded digital data (i.e. a series of information formed of 0 and 1) based on the different reflection result.
At present, the development of CD technology advances to be a DVD (digital versatile disk) with a capacity up to several GBs and capable of storing a movie program. When playing the audio/video program, a subtitle is also displayed on the bottom of a screen. The conventional method of displaying a subtitle is described below. With reference to FIG. 1A, it shows a block diagram for a conventional display flow of the single subtitle. In fact, the playing of the DVD is performed by sequentially pasting stored images on the screen. For example, a single subtitle package corresponding character A and the rest blank area of the screen is read from a recording medium R1 and then decoded to be a subtitle video S1 displayed on the screen. In the mean time, a background package A/V (Audio/Video) is read from the recording medium R1, and a decoded background video B1 (its corresponding image includes a cloud 2 and a horse) is displayed on the screen, and the subtitle video S1 and the background video B1 are overlaid by the use of a synthesizer M to form an output video O1. Next, with reference to FIG. 1B, it shows a schematic block diagram of a conventional switching display flow of a plurality of subtitles, wherein FIG. 1A's corresponding subtitle data structure on the recording media is shown in the bottom figure of FIG. 1B. For example the display time of character A starts from tAs and ends at tAe, this period of time is called presenting time stamp (PTS) which is stored in a header of a package F-P1 for displaying an image 1. Similarly, the display time of character B starts from tBs and ends at tBe, and the display time are stored in a header of a package F-P2 for displaying an image 2. As shown in FIG. 1A, the conventional subtitle video S1 of the character A and the decoded background video B1 are overlaid through a first synthesizer M1 to form a first output video O1. Next, when the time axis runs to tAe, the first output video O1 is erased by a first eraser E1, and the display flow of another character B is repeated. That is, a single subtitle package for displaying the character B and the rest blank area of the screen are read from the recording medium, as well as the decoded subtitle video S2 and the decoded background video B1 are overlaid by a second synthesizer M2 to form a second output video O2 that is to be displayed on the screen. However, according to the PTS of the character B, its display is terminates and the character B disappears (executed by a second eraser) at tBe, and eventually only the background video is output as a third output video O3. As obviously shown in FIG. 1B, the subtitle video S1 has the same image structure as the subtitle video S2, i.e. within the whole substrate frame 1 (as shown by a dash line), the rest area except the character A or B is all blank. Since the blank area in the screen also requires blank pixel information corresponding to the blank area to be encoded and compressed into the DVD, therefore the capacity of the medium (for example DVD) for storing the subtitle is significantly increased.
To solve the problem of the conventional technology, therefore it is necessary to provide a medium for storing the subtitle data structure of an audio/video program, and the medium can significantly reduce the capacity needed to store the subtitle. Moreover, there exists a need for a method of playing the subtitle of the audio/video program.